Pasted from dell web site
DDR Memory Overview
DDR memory modules should be installed in pairs of matched memory size. This means that if you purchased your computer with 128 MB of memory installed and you want to add another 128 MB of memory, you should install it in the appropriate connector. If the DDR memory modules are not installed in matched pairs, the computer will continue to operate, but with a slight reduction in performance.
Chat with Dell support
He said as long as I got the same speed (MHz) the size (Mb) wouldn't matter. It wouldn't run with a slight reduction in performance as stated above. Even if I had 1 PC3200 256 and 1 PC3200 512.
A person there told me that. I would need to have identical cards (Mb and MHz). If I didn't have the same size I would have 15% - 25% lose of performance. This is not what deal support chat person told me.
Called Dell support on the phone
This person said that the chat person was correct. But, Later in the phone call told me I needed another PC3200 256 to match the one I have.
So now you know why I'm confused. I got a couple of different answers. I had a PC2100 from my last system. I was wanting to use it. But didn't know if it would make my system run slower because of the speed.
I have a couple of question for you people now.
a. Will the PC2100 256 installed with the one that came installed make my system slower?
b. Do these have to be identical cards? Or do they just need to be the same MHz and the Mb not matter like the first person told me?
c. I know this might be a stupid question. But I just need to ask.
If the card do have to be the same size and speed does it have to be made by the same company?
Thanks for the help.